Help! Lost O2 Sensor threads

[ohecht]

Does anyone know the size and pitch of the standard Bosch O2 sensor? Bosch part 11027, specifically.

I need to retap the threads and I can't find anything at any local hardware store that fits the threads.

It seems like either 11/16 SAE, 17mm or 18mm. No idea on the thread pitch.

If I do have to ream out the hole, is there a Bosch sensor that has threads slightly larger?

I need to do something about that hole in my SSIs.

Thanks,

Olivier

[nhromyak]

Go to your local muffler shop. For ~$20.00 they should be able to retap the theads. Worse case - they will cut the original hole out and weld on an O2 bung hole.

I went to Midas, they wanted $70.00 to cut a hole, and weld on an O2 hole!

I went to my local muffler independent - $20.00.

If you want to weld it on yourself, go to your local muffler guy, bud around with him for a bit, he might GIVE you one. Or he will sell one o you for $5.00.

[ohecht]

I thought about that, but the P.O. had one welded on rather sloppily already, so I wonder about whether they could get a new one in the same place without destroying the SSIs. There is a huge "glob" of steel around the current hole. I have no welding experience.

Also, does the fact that the O2 sensor does not technically belong there matter? I have run into muffler shop before that would not work on anything that wasn't 100% stock involving emmissions systems, etc.

Olivier

[nhromyak]

My independents didn't care about stock exhaust or emissions.... They just wanted $$$. You should be all set to go, especially if you have cash. Call around, try to tell them exactly what you have, what you want to do, and try to speak there language (02 bung hole, etc.)

I think the Midas guy was a little leary. But DANG!!! three times as much!?!?!?

Of course, it's Sunday. The day we all try to finish these large projects (ask me what I did LAST weekend - rear suspension), and no one is open.

Good Luck.

[ohecht]

It looks like I will be able to recut the threads in the existing bung-hole.

Do you know what the threads are for the inserts shops carry?

Thanks,

Olivier

[89911]

This would explain why your sensor galled. Most likely he used a cheaper steel that bonded with the sensor. I had this happen to a bypass pipe in only a few months. I had the threads retapped and then sold it. You don't need tons of torque on this bolt so as long as you have enough threads, your ok.

[ohecht]

I got lucky. The threads are 18mm X 1.5mm, and that just happens to be the size of the used tap I found lying in a tote in the back of the hardware store on Sunday afternoon!

It was the only metric tap in the whole place and the guy gave it to me for $4.

For some reason, I thought it was a 19mm, so I spent Sunday night researching other places for large metric taps.

On my way to work in the morning and later to the hardware store across town, I decided to check the size of the tap I just got, and it was the exact right size.

Too late to repair that morning, but the new threads and sensor went in fine last night. I got lucky and all it cost me was the threads on the first new sensor.

If anyone has a way to clean up the mashed threads on the sensor and make it work, you're welcome to have it.

Olivier

[fred cook]

Sorry that I didn't see this sooner. As you found out, the O2 threads are the same as a standard spark plug thread. Most auto parts stores carry a combination re-threading tool for around $10
or less. It is the small thread on one end, large thread on the other with a hex section in the center. Work slowly, use some cutting oil and you should be back together quickly. A lot quicker and cheaper than cutting and welding!

Fred Cook
80 911SC

[ohecht]

I did see a couple of those before I was sure of the size. By the time I figured it out, I had already lucked into the regular tap.

The tapping of the new threads went surprisingly well. I hate the feeling at the beginning as you try to keep everything lined up in tight locations.

Olivier